The present day extensive use of wireless communications, for example with cellular telephones, presents new problems in system maintenance. With the large number of antennas necessary to meet the present and growing demand for coverage, even the routine inspection of antennas becomes costly and time consuming. Because of coverage needs, many antennas are placed in remote locations and in locations which are relatively difficult to access and this increases the difficulty for regular inspections needed for system maintenance.
Normally, antennas are impedance matched to the connected transmitter or receiver to provide maximum power transfer to and from the antenna. When an antenna is damaged it becomes mismatched and power is reflected from the connection. For a transmit antenna, power is reflected back to the transmitter. This reflected power is generally large and can be detected by special hardware to determine that the antenna is mismatched and possibly damaged.
For a receive antenna with a mismatch, the amount of power transferred to the receiver is reduced. Thus the receiver does not have a direct indication of its antenna's mismatch. Power can be transmitted to the receive antenna and the reflected power measured to determine a mismatch. However, up to the present time, because received communication signals have low power, the receiver would always have to shut off during the measurement process since the transmitted power of the measurement system would interfere with the low power received communication signals.